The present invention relates to a method of rolling cigarette portions.
In the tobacco industry, filter-tipped cigarettes are known to be formed using a method comprising the steps of forming, on a manufacturing machine, a continuous cigarette rod of tobacco enclosed in a tubular wrapping; cutting double cigarette portions off the cigarette rod, i.e. cigarette portions twice the length of the cigarette portion of a finished filter-tipped cigarette; and transferring the double cigarette portions to the input drum of a filter-assembly machine by means of a transfer device. On the filter-assembly machine, the double cigarette portions are arranged parallel and fed, in a single orderly succession and in a direction crosswise to their respective axes, to a cutting station where they are cut in half into pairs of single cigarette portions still arranged in said orderly succession. The single cigarette portions in each pair are then parted a given distance to receive, in between, a double filter and a band projecting between the two cigarette portions, and so form a group comprising a double filter, two single cigarette portions on either side of the double filter, and a projecting band. Each group is then rolled along a rolling path to wind the band about the double filter and respective ends of the single cigarette portions, and so form a double filter-tipped cigarette, which is then cut in half into a pair of single filter-tipped cigarettes.
Though still used successfully on many currently marketed machines, the above method is limited on account of rolling the groups along a rolling path resulting in tobacco fallout from the ends of the cigarette portions; which fallout is directly proportional to the rolling speed of the groups, and is therefore kept within acceptable limits by reducing the rolling speed and hence the output of the filter-assembly machine.
Increasing output by reducing the spacing of the groups is only possible up to a certain point, which is determined by the length of the projecting band, and beyond which one group would be superimposed on the band of the preceding group.
To overcome this drawback, Patent Application GB-A-2302791 provides for feeding a succession of double cigarette portions along a given plane to a cutting station where the double cigarette portions are cut to form a succession of pairs of single cigarette portions in said plane. The succession of pairs of single cigarette portions is then divided into two orderly successions, which are fed along separate superimposed planes for supply, together with respective double filters and respective bands, to respective superimposed rolling tracks to form two separate successions of double cigarettes.
This solution provides for high output of the filter-assembly machine, while at the same time halving rolling speed and so maintaining an acceptable degree of tobacco fallout. On the other hand, feeding the two successions of pairs of single cigarette portions along separate, substantially superimposed planes calls for at least three additional drums--as compared with a conventional filter-assembly machine with a rolling path extending in a single plane--thus complicating the design and increasing the production cost of the filter-assembly machine.
An alternative solution in U.S. Pat. No. 4,841,993 provides for supplying a filter-assembly machine with two parallel orderly successions of side by side double cigarette portions; cutting the double cigarette portions into pairs of single cigarette portions arranged in said two parallel orderly successions, in which each pair in one succession is coaxial with a pair in the other succession; supplying the respective filters and bands to form groups arranged in said two successions; and rolling the groups along a common rolling path to form two successions of double cigarettes.
Alongside the advantages provided by the above mentioned method, the same method also involves several drawbacks by calling for twice the axial length of the rolling drum and rolling track, thus resulting in problems as regards support of the drum--which, as is known, projects to allow troublefree access to the components of the filter-assembly machine--and the precision with which the groups are rolled. In other words, a long drum calls for highly accurate supports to prevent misalignment of the drum, and wear of the supports rapidly impairs precision, thus resulting in damage to the cigarette portions in direct proportion to the distance between the cigarette portions and the support.